Among semiconductor manufacturing apparatuses such as a film formation device, there is a batch-type semiconductor manufacturing apparatus that processes a plurality of semiconductor wafers simultaneously. A conventional batch-type semiconductor manufacturing apparatus introduces source gas, reactant gas, or the like in a vacuum chamber and exhausts these gas from a bottom portion of the chamber.
However, in such a case, a gas retention time in a top portion of the chamber is longer than that in the bottom portion thereof. That is, gas concentration in the top portion of the chamber is higher than that in the bottom portion thereof. For this reason, the film thickness of a material formed on a semiconductor wafer varies depending on the position of the semiconductor wafer within the chamber. For example, a relatively thin film is formed on a semiconductor wafer arranged in the bottom portion of the chamber, and a relatively thick film is formed on a semiconductor wafer arranged in the top portion of the chamber.
To suppress such a variation in the film thickness, it is conceivable that temperatures of respective portions in the chamber are adjusted. However, when process temperatures are changed, the film quality (for example, stress and the like) also changes. Accordingly, in the conventional batch-type semiconductor manufacturing apparatus, it has been difficult to uniformize the film thickness and the film quality among semiconductor wafers.